Silicon oxide has been a material of great utility in the technology of silicon devices. In many of its uses in this technology, there is a need for patterning the silicon oxide, and more particularly to providing in a silicon oxide layer openings with essentially vertical side walls.
Presently, the standard technique for forming such openings involves providing over the oxide layer a mask having a pattern of openings matching that desired for the oxide layer openings and then etching the exposed portions of the layer anisotropically by reactive ion etching (RIE). This process requires expensive equipment with low throughput so that it becomes slow and costly.
It is desirable to form openings in a silicon oxide layer without the need for expensive equipment that has a low throughput.
It is known to use wet etchants to pattern layers in silicon oxide but generally such etching is isotropic and this gives rise to undercutting of the mask used to define the pattern. As a result, the side walls of the openings formed are sloped.
Moreover, while some crystalline materials can be etched along selected crystal planes to provide anisotropy, this is not usually possible because of the generally amorphous nature of the silicon oxide layers used in silicon device technology.
It has also long been known that regions of most materials damaged by irradiation by high energy particles can be etched faster than undamaged regions but this approach has not been used to any significant extent in the processing of silicon devices.